Installed version: "1.3.1+1"

: Error: Method 'insert' cannot be called on 'OverlayState?' because it is potentially null.
../…/lib/zoom_pinch_overlay.dart:232
- 'OverlayState' is from 'package:flutter/src/widgets/overlay.dart' ('../../../flutter/packages/flutter/lib/src/widgets/overlay.dart').
package:flutter/…/widgets/overlay.dart:1
    Try calling using ?. instead.
          overlayState.insert(_overlayEntry!);
                       ^^^^^^

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Details:

• This adds a modal barrier in the background (like in dialogs for example) and the user can set the color of that barrier to make it more customizable.

In this PR I have also made a refactor of the code to make it look cleaner

• constructors always first.
• avoid lines longers than 80 lines.
• add missing trailing commas.
• use cascade.
• use final in values that doesn't change.
• omit type annotation.
• async functions now has the type Future

Describe the bug I have the ZoomOverlay used in a Column widget, and when I don't set the twoTouchOnly property to true, the widget glitches quickly, bounces back to the original location and produces an error:

I/flutter (23218): ══╡ EXCEPTION CAUGHT BY ANIMATION LIBRARY ╞═════════════════════════════════════════════════════════ I/flutter (23218): The following _CastError was thrown while notifying listeners for AnimationController: I/flutter (23218): Null check operator used on a null value I/flutter (23218): I/flutter (23218): When the exception was thrown, this was the stack: I/flutter (23218): #0 _ZoomOverlayState.initState. (package:zoom_pinch_overlay/zoom_pinch_overlay.dart:92:36) I/flutter (23218): #1 AnimationLocalListenersMixin.notifyListeners (package:flutter/src/animation/listener_helpers.dart:136:19) I/flutter (23218): #2 AnimationController.value= (package:flutter/src/animation/animation_controller.dart:366:5) I/flutter (23218): #3 AnimationController.reset (package:flutter/src/animation/animation_controller.dart:385:5) I/flutter (23218): #4 _ZoomOverlayState.onScaleEnd (package:zoom_pinch_overlay/zoom_pinch_overlay.dart:176:22) I/flutter (23218): #5 ScaleGestureRecognizer._reconfigure. (package:flutter/src/gestures/scale.dart:465:53) I/flutter (23218): #6 GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:182:24) I/flutter (23218): #7 ScaleGestureRecognizer._reconfigure (package:flutter/src/gestures/scale.dart:465:11) I/flutter (23218): #8 ScaleGestureRecognizer.handleEvent (package:flutter/src/gestures/scale.dart:388:36) I/flutter (23218): #9 PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:93:12) I/flutter (23218): #10 PointerRouter._dispatchEventToRoutes. (package:flutter/src/gestures/pointer_router.dart:138:9) I/flutter (23218): #11 _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:397:8) I/flutter (23218): #12 PointerRouter._dispatchEventToRoutes (package:flutter/src/gestures/pointer_router.dart:136:18) I/flutter (23218): #13 PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:122:7) I/flutter (23218): #14 GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:439:19) I/flutter (23218): #15 GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:419:22) I/flutter (23218): #16 RendererBinding.dispatchEvent (package:flutter/src/rendering/binding.dart:287:11) I/flutter (23218): #17 GestureBinding._handlePointerEventImmediately (package:flutter/src/gestures/binding.dart:374:7) I/flutter (23218): #18 GestureBinding.handlePointerEvent (package:flutter/src/gestures/binding.dart:338:5) I/flutter (23218): #19 GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:296:7) I/flutter (23218): #20 GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:279:7) I/flutter (23218): #24 _invoke1 (dart:ui/hooks.dart:182:10) I/flutter (23218): #25 PlatformDispatcher._dispatchPointerDataPacket (dart:ui/platform_dispatcher.dart:282:7) I/flutter (23218): #26 _dispatchPointerDataPacket (dart:ui/hooks.dart:96:31) I/flutter (23218): (elided 3 frames from dart:async) I/flutter (23218): I/flutter (23218): The AnimationController notifying listeners was: I/flutter (23218): AnimationController#e9df8(⏮ 0.000; paused) I/flutter (23218): ════════════════════════════════════════════════════════════════════════════════════════════════════

A workaround is to set this field to true; but the same error will appear if you then try to use 3 fingers instead of just 2.

To Reproduce

Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        Padding(
          padding: const EdgeInsets.only(top: 16.0),
          child: Center(
            child: AspectRatio(
              aspectRatio: kImageAspectRatio,
              child: ZoomOverlay(
                minScale: 0.5,
                maxScale: 3.0,
                child: ClipRRect(
                  borderRadius: BorderRadius.circular(6),
                  child: CachedNetworkImage(
                    imageUrl: imageUrl!,
                    fadeInCurve: Curves.easeInOutSine,
                    placeholder: (context, _) =>
                        const ImageLoadingPlaceholder(),
                  ),
                ),
              ),
            ),
          ),
        ),
        caption,
      ],
    );

Expected behavior The widget should zoom without an error, no matter if I set the twoTouchOnly property.

Smartphone (please complete the following information):

• Flutter (Channel stable, 2.2.3, on macOS 11.5 20G71 darwin-arm)
• zoom_pinch_overlay: 1.1.2
• Device: Samsung S21
• OS: Android 11

First of all great job on this plugin. I am the developer of a similar plugin called pinch_zoom, but I was always struggling with some issues that this plugin doesn't have. Only one issue that my plugin managed to solve by using the InteractiveViewer, this plugin still has. Hopefully you might know a solution to this.

Describe the bug When zooming in on an image in a PageView, the page will change instead of the image zooming in. Possibly this could be resolved using the OneSequenceGestureRecognizer or MultiDragGestureRecognizer. In my plugin I managed to solve this even more when using the answer provided in https://stackoverflow.com/questions/51712287/how-to-disable-multi-touch-in-mobile-application-using-flutter/56037327#56037327, which I had to use since I couldn't solve the issue using GestureRecognizer solutions, simply since my plugin uses the InteractiveViewer and not that one.

To Reproduce Steps to reproduce the behavior:

1. Add a PageView.builder() with multiple pages
2. Add an image wrapped by the ZoomOverlay() to one of these pages
3. Try zooming in on this image. Try with both more vertical and horizontal zooming.
4. Though it works better with twoTouchOnly, you shall notice that the PageView tends to have priority over the zooming of the ZoomOverlay(). It also works better when zooming vertically.

Expected behavior The image will zoom in instead of the page changing